Therapeutic potential of FLT4-targeting peptide in acute myeloid leukemia

Abstract

Fms-related tyrosine kinase-4 (FLT4) is involved in tumor progression. Previously, we found that dysfunctional natural killer (NK) cells with low interferon-gamma (IFN-γ) were restored in acute myeloid leukemia (AML) by the FLT4 antagonist MAZ51. In this work, we developed 12 peptides targeting FLT4 for clinical application and ultimately selected 4 of them to examine whether they restored the frequency of lymphocytes, especially T cells and NK cells, and high IFN-γ expression, as MAZ51 treatment did in our previous study. Although clinical data from using intracellular kinase domain-targeting peptides are currently available, peptides targeting FLT4 to modulate immune cells have not been fully elucidated. In this study, we focus on novel peptide 4 (P4) from the intracellular domain of FLT4 because it had dominant negative activity. Similar to MAZ51, high IFN-γ levels were expressed in AML-mononuclear cells (MNCs) exposed to P4. In addition, T and NK cell levels were restored, as were high IFN-γ levels, in a leukemic environment when P4 was co-cultured with cytosine β-D-arabinofuranoside. Interestingly, the frequency of regulatory T cells was signi cantly decreased by P4, implying that the peptide plays a role in modulating the tumor niche. Overall, we demonstrated the therapeutic value of functionally modulating lymphocytes using a peptide targeting FLT4 and propose the development of advanced therapeutic approaches against AML by using immune cells.